Soils are generally accepted as sinks for microplastics (MPs) but at the same time might be an MP source for inland waters. However, little is known regarding the potential MP delivery from soils to aquatic systems via surface runoff and erosion. This study provides, for the first time, an estimate of the extent of soil-erosion-induced MP delivery from an arable-dominated mesoscale catchment (390 km2) to its river network within a typical arable region of southern Germany. To do this, a soil erosion model was used and combined with the potential particular MP load of arable land from different sources (sewage sludge, compost, atmospheric deposition, and tyre wear) from 1950 onwards. The modelling resulted in an annual mean MP flux into the stream network of 6.33 kg MP a−1
Up-to-date digital soil resource information and its comprehensive understanding are crucial to supporting crop production and sustainable agricultural development. Generating such information through conventional approaches consumes time and resources, and is difficult for developing countries. In Ethiopia, the soil resource map that was in use is qualitative, dated (since 1984), and small scaled (1 : 2 M), which limit its practical applicability. Yet, a large legacy soil profile dataset accumulated over time and the emerging machine-learning modeling approaches can help in generating a high-quality quantitative digital soil map that can provide better soil information. Thus, a group of researchers formed a Coalition of the Willing for soil and agronomy data-sharing and collated about 20 000 soil profile data and stored them in a central database. The data were cleaned and harmonized using the latest soil profile data template and 14 681 profile data were prepared for modeling. Random forest was used to develop a continuous quantitative digital map of 18 World Reference Base (WRB) soil groups at 250 m resolution by integrating environmental covariates representing major soil-forming factors. The map was validated by experts through a rigorous process involving senior soil specialists or pedologists checking the map based on purposely selected district-level geographic windows across Ethiopia. The map is expected to be of tremendous value for soil management and other land-based development planning, given its improved spatial resolution and quantitative digital representation.
The influence of mineral dust deposition on soil formation in the mountain critical zone was evaluated at six sites in southwestern North America. Passive samplers collected dust for 2 years, and representative soil and rock were gathered in the vicinity of each dust sampler. All materials (dust, soil, and rock) were analyzed to determine their mineralogy (with X-ray diffraction), geochemistry (with inductively coupled plasma mass spectrometry (ICP-MS)), and radiogenic isotope fingerprint (
Conservation agriculture (CA), combining reduced or no tillage, permanent soil cover, and improved rotations, is often promoted as a climate-smart practice. However, our understanding of the impact of CA and its respective three principles on top- and subsoil organic carbon stocks in the low-input cropping systems of sub-Saharan Africa is rather limited. This study was conducted at two long-term experimental sites established in Zimbabwe in 2013. The soil types were abruptic Lixisols at Domboshava Training Centre (DTC) and xanthic Ferralsol at the University of Zimbabwe farm (UZF). The following six treatments, which were replicated four times, were investigated: conventional tillage (CT), conventional tillage with rotation (CTR), no tillage (NT), no tillage with mulch (NTM), no tillage with rotation (NTR), and no tillage with mulch and rotation (NTMR). Maize (Zea maysVigna unguiculatap<0.05) higher in the NTM, NTR and NTMR treatments compared with the NT and CT treatments in the top 5 cm and top 10 cm layers at UZF, while SOC stocks were only significantly higher in the NTM and NTMR treatments compared with the NT and CT treatments in the top 5 cm at DTC. NT alone had a slightly negative impact on the top SOC stocks. Cumulative SOC stocks were not significantly different between treatments when considering the whole 100 cm soil profile. Our results show the overarching role of crop residue mulching in CA cropping systems with respect to enhancing SOC stocks but also that this effect is limited to the topsoil. The highest cumulative organic carbon inputs to the soil were observed in NTM treatments at the two sites, and this could probably explain the positive effect on SOC stocks. Moreover, our results show that the combination of at least two CA principles including mulch is required to increase SOC stocks in these low-nitrogen-input cropping systems.
Soil structure is sensitive to intensive soil management. It can be ameliorated by a reduction in soil cultivation and stimulation of plant and microbial mediators for aggregate formation, with the latter being a prerequisite and measure for soil quality. Cover crops (CCs) are part of an integrated approach to stabilize or improve soil quality. Thereby, the incorporation of diverse CC mixtures is hypothesized to increase the positive effects of CC applications. This study entailed an investigation of the legacy effect of CCs on soil aggregates after three crop rotations in the second main crop (winter wheat) after the last CC treatment. Four CCs (mustard, phacelia, clover, and oat) cultivated in pure stands and with a fallow treatment were compared to a mixture of the four CC species (Mix4) and a highly diverse 12-plant-species mixture (Mix12) in a long-term field experiment in Germany. The organic carbon (OC) distribution within macroaggregate fractions (16–8, 8–4, 4–2, 2–1, and <1 mm) and their aggregate stability were measured by dry- and wet-sieving methods, and the mean weight diameter (MWD) was calculated from water-stable aggregates.
The results showed that, compared to the fallow, all CCs increased the MWD between 10 % and 19 % in soil under the following main crop. The average MWD increase over the fallow was slightly higher for CC mixtures (16 %) than for single CCs (12 %). Most of the OC (67.9 % on average) was stored in the <1 mm aggregate fraction, highest in the topsoil and decreasing with soil depth. The intermediate fractions (8–4 mm, 4–2 mm, 2–1 mm) stored 8.5 %, 10.5 %, and 11.0 % of the total OC, while 2.1 % was stored in the 16–8 mm fraction. Higher MWD improvement at the 20–30 cm depth also indicates additional benefits from a reduction in the cultivation depth. Structural equation modelling (SEM) suggests that single CCs were more likely to increase OC storage in small macroaggregates <1 mm, while CC mixtures were more likely to increase OC in the largest fraction (8–16 mm). Different individual CC species or mixtures exhibited varying involvement in the formation of different aggregate fractions. We provide evidence that litter quality, root morphology, and rhizosphere input, which affect microbial mediators of aggregate formation, might be the main reasons for the observed differences between CC treatments. Cover crops are valuable multifunctional tools for sustainable soil management. Here, we showed that they contribute to structure amelioration in arable soils. Increasing the functional diversity of plant species in CC mixtures could be a strategy to further enhance the positive effects of CCs in agroecosystems.In a context of accelerated soil erosion and sediment supply to water bodies, sediment fingerprinting techniques have received an increasing interest in the last 2 decades. The selection of tracers is a particularly critical step for the subsequent accurate prediction of sediment source contributions. To select tracers, the most conventional approach is the three-step method, although, more recently, the consensus method has also been proposed as an alternative. The outputs of these two approaches were compared in terms of identification of conservative properties, tracer selection, modelled contributions and performance on a single dataset. As for the three-step method, several range test criteria were compared, along with the impact of the discriminant function analysis (DFA).
The dataset was composed of tracer properties analysed in soil (three potential sources; n = 56) and sediment core samples (n = 32). Soil and sediment samples were sieved to 63 µm and analysed for organic matter, elemental geochemistry and diffuse visible spectrometry. Virtual mixtures (n = 138) with known source proportions were generated to assess model accuracy of each tracer selection method. The Bayesian un-mixing model MixSIAR was then used to predict source contributions on both virtual mixtures and actual sediments.The different methods tested in the current research can be distributed into three groups according to their sensitivity to the conservative behaviour of properties, which was found to be associated with different predicted source contribution tendencies along the sediment core. The methods selecting the largest number of tracers were associated with a dominant and constant contribution of forests to sediment. In contrast, the methods selecting the lowest number of tracers were associated with a dominant and constant contribution of cropland to sediment. Furthermore, the intermediate selection of tracers led to more balanced contributions of both cropland and forest to sediments.The prediction of the virtual mixtures allowed us to compute several evaluation metrics, which are generally used to support the evaluation of model accuracy for each tracer selection method. However, strong differences or the absence of correspondence were observed between the range of predicted contributions obtained for virtual mixtures and those values obtained for actual sediments. These divergences highlight the fact that evaluation metrics obtained for virtual mixtures may not be directly transferable to models run for actual samples and must be interpreted with caution to avoid over-interpretation or misinterpretation. These divergences may likely be attributed to the occurrence of a not (fully) conservative behaviour of potential tracer properties during erosion,Future research should develop novel metrics to quantify the conservative behaviour of tracer properties during erosion and transport processes. Furthermore, new methods should be designed to generate virtual mixtures closer to reality and to better evaluate model accuracy. These improvements would contribute to the development of more reliable sediment fingerprinting techniques, which are needed to better support the implementation of effective soil and water conservation measures at the catchment scale.Woody-plant encroachment into grasslands and savannas has been globally widespread during the past century, likely driven by interactions between grazing, fire suppression, rising atmospheric CO2, and climate change. In the southernmost US Great Plains, Ashe juniper and live oak have increased in abundance. To evaluate potential interactions between this vegetation change and the underlying soil parent material on ecosystem biogeochemistry, we quantified soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and δ13Cδ13C−19 ‰, whereas those under woody patches were −21 ‰ to −24 ‰, indicating that wooded areas were relatively recent components of the landscape. Compared with grasslands, areas now dominated by juniper or oak had elevated SOC, TN, and TP storage in soils lying atop Edwards limestone. In Buda soils, only oak patches had increased SOC, TN, and TP storage compared with grasslands. Woody encroachment effects on soil nutrients were higher in soils on the Edwards formation, perhaps because root and litter inputs were more concentrated in the relatively shallow layer of soil atop the Edwards bedrock. Our findings suggest that geological factors should be considered when predicting nutrient store responses in savannas following vegetation change. Given that woody encroachment is occurring globally, our results have important implications for the management and conservation of these ecosystems. The potential interactive effects between vegetation change and soil parent material on C, N, and P storage warrant attention in future studies aimed at understanding and modeling the global consequences of woody encroachment.
Sorption of mercury (Hg) in soils is suggested to be predominantly associated with organic matter (OM). However, there is a growing collection of research that suggests that clay minerals and
Soil erosion, considered a major environmental and social problem, leads to the loss of soil nutrients and the degradation of soil structure and impacts plant growth. However, data on the effects of land use changes caused by vegetation restoration on soil nutrients and erodibility for different slope aspects are limited. This study was conducted to detect the response of soil nutrients and erodibility to slope aspect in a typical watershed in the northern agro-pastoral ecotone in China. The following indexes were used to determine the improvement in soil nutrients and erodibility through a weighted summation method: the comprehensive soil nutrient index and the comprehensive soil erodibility index. The results showed that the vegetation types with the highest comprehensive soil quality index (CSQI) values on western, northern, southern, and eastern slopes were Pinus sylvestrisAstragalus melilotoidesCaragana korshinskiiCapillipedium parviflorumAstragalus melilotoidesCaragana korshinskiiLespedeza bicolorC. korshinskiiL. bicolor, were the optimal selection to improve soil nutrients and soil erodibility for any slope aspect.
Long-term excessive application of mineral fertilizer leads to phosphorus (P) accumulation, increasing the risk of P migration and loss from the soil profile. The colloids in the soil profile are important carriers for P migration due to their high P adsorption and transport capacity. It is not clearly understood how colloidal P (CP) is distributed in subsoils (<1.2 m) of a Vertisol, contributing to subsurface P loss. Understanding the depth sequence distribution and speciation of colloidal P in the soil profile is critical for a comprehensive assessment of P loss. In this study, water-extractable colloids (WECs) with the size of 0.35–2 µm were obtained from a 0–120 cm soil profile by a sedimentation and centrifugation scheme. The dissolved reactive P (DRP) and dissolved total P (DTP) in soil supernatant with particle sizes <0.35 µm were measured by molybdate blue colorimetry. Solution 31P nuclear magnetic resonance (NMR) and P K-edge XANES (X-ray absorption near-edge structure) were used to characterize the species and distribution of CP in the soil profile of fertilized farmland. Total and available P in bulk soil and colloids decreased with soil depth. The organic P (OP) contained 97–344 mg kg−1−1<2 µm was about 38–93 mg P kg−1
Soil aggregation is an important process in nearly all soils across the globe. Aggregates develop over time through a series of abiotic and biotic processes and interactions, including plant growth and decay, microbial activity, plant and microbial exudation, bioturbation, and physicochemical stabilization processes, and are greatly influenced by soil management practices. Together, and through feedback with organic matter and primary soil particles, these processes form dynamic soil aggregates and pore spaces, which jointly constitute a soil's structure and contribute to overall soil functioning. Nevertheless, the concept of soil aggregates is hotly debated, leading to confusion about their function or relevancy to soil processes. We argue here that the opposition to the concept of soil aggregation likely stems from the fact that the methods for the characterization of soil aggregates have largely been developed in the context of arable soils, where tillage promotes the formation of distinct soil aggregates that are easily visible in the topsoil. We propose that the widespread use of conceptual figures showing detached and isolated aggregates can be misleading and has contributed to the skepticism towards soil aggregates. However, the fact that we do not always see discrete aggregates within soils in situ does not mean that aggregates do not exist or are not relevant to the study of soil processes. Given that, by definition, soil aggregates consist of any group of soil particles that cohere more strongly to each other than neighboring particles, aggregates may, but do not necessarily need to be, bordered by pore space. Here, we illustrate how aggregates can form and dissipate within the context of undisturbed, intact soils, highlighting the point that aggregates do not necessarily need to have a discrete physical boundary and can exist seamlessly embedded in the soil. We hope that our contribution helps the debate on soil aggregates and supports the foundation of a shared understanding on the characterization and function of soil structure.
Ameliorating soil acidity using a combination of lime and organic amendments (OAs) can be an alternative to lime alone, but determining the appropriate OA rates can be difficult. We developed a new method for calculating the combined application rate of lime and OAs (wheat straw, faba bean straw, blended poultry litter, biochar, and compost) that is based on the titratable alkalinity of OAs and the equilibrium lime buffer capacity (LBCeq) of acidic soils. The effect of calculated soil amendment rates on soil pH was validated at soil water contents of 60 %, 100 %, and 150 % of field capacity (FC). The soil used to develop and validate the method was a sandy loam with a soil pH in deionised water (pHW) of 4.84 and a soil pH in 0.01 M CaCl2Ca) of 4.21. The LBCeq3 kg−1 pH−13 kg−1 pH−1” denotes the amount of lime required to raise the pH of 1 kg of soil by one unit). The titratable alkalinity of the OAs ranged from 11.7 cmol H
An assessment of the soil and bedrock thermal structure of the Sierra de Guadarrama, in central Spain, is provided using subsurface and ground surface temperature data coming from four deep (20 m) monitoring profiles belonging to the Guadarrama Monitoring Network (GuMNet) and two shallow profiles (1 m) from the Spanish Meteorology Service (Agencia Estatal de Meteorología, AEMET) covering the time spans of 2015–2021 and 1989–2018, respectively. An evaluation of air and ground surface temperature coupling showed that soil insulation due to snow cover is the main source of seasonal decoupling, being especially relevant in winter at high-altitude sites. Temperature propagation in the subsurface was characterized by assuming a heat conductive regime by considering apparent thermal diffusivity values derived from the amplitude attenuation and phase shift of the annual cycle with depth. This methodology was further extended to consider the attenuation of all harmonics in the spectral domain, which allowed for analysis of thermal diffusivity from high-frequency changes in the soil near the surface at short timescales. For the deep profiles, the apparent thermal diffusivity ranges from 1 to
Availability of reactive nitrogen (Nr) is a key control on carbon (C) sequestration in wetlands. To complement the metabolic demands of Sphagnumr2rSphagnum-dominated bogs in polluted regions, indicating the adaptation of N215N2-tracer experiment was combined with a natural-abundance N-isotope study at three Sphagnum-dominated peat bogs in the northern Czech Republic in an attempt to assess the roles of individual BNF drivers. High short-term BNF rates (8.2 ± 4.6 g N m2 d−1) were observed at Malé mechové jezírko, which receives ∼ 17 kg Nr ha−1 yr−1. The remaining two peat bogs, whose recent atmospheric Nr−1 yr−1
Soil organic matter (SOM) plays an important role in the global carbon cycle, especially in alpine ecosystems. However, ongoing forest expansion in high-elevation systems potentially alters SOM storage through changes in organic matter (OM) inputs and microclimate. In this study, we investigated the effects of an Picea abies L. afforestation chrono-sequence (0 to 130 years) of a former subalpine pasture in Switzerland on soil organic carbon (SOC) stocks and SOM dynamics. We found that SOC stocks remained constant throughout the chrono-sequence, with comparable SOC stocks in the mineral soils after afforestation and previous pasture (SOC forest40 = 11.6 ± 1.1 kg m−2, SOC forest130 = 11.0 ± 0.3 kg m−2= 11.5 ± 0.5 kg m−2). However, including the additional carbon of the organic horizons in the forest, reaching up to 1.7 kg m−2C:Ncm) with increasing forest stand age, from 11.9 ± 1.3 in the pasture to 14.3 ± 1.8 in the 130-year old forest. In turn, we observed a decrease in the soil C:NC:N± 1.9 to 42.4 ± 10.8) is likely to be incorporated and translocated from the organic horizon to the mineral topsoil (0–10 cm) of the profiles. Due to the high root C:N± 2.8 and forests between 54.7 ± 3.9 and 61.2 ± 2.9), particulate root-derived organic matter seems to have a rather small effect on forest soil C:N
The introduction of innovative technologies in agriculture is key not only to improving the efficiency of agricultural production and crop yields and quality but also to balancing energy use and preserving a cleaner environment. Biopreparations are environmentally friendly means of restoring the vitality of the soil in which plants can thrive. Biopreparations have an impact on soil health and alter greenhouse gas emissions. The aim of this study was to investigate the effects of different biopreparations on soil porosity, temperature, and CO2222AzospirillumFrateuria aurentia, Bacillus megaterium, mineral oils, Azotobacter vinelandi, humic acid, gibberellic acid, sodium molybdate, Azototbacter chroococcum, Azospirillum brasilense, etc. Evaluating the effectiveness of biopreparations on soil porosity, temperature, and CO2Azotobacter chroococcum, Azotospirilum brasilense, various herbs, marine algae extracts, oils of plants, and mineral substances. The multiple-regression model showed that soil temperature has a greater influence on the variation of CO2
We evaluated the performance of a new, simple test to evaluate soil structural stability. The QuantiSlakeTest (QST) consists in a quantitative approach of the slake test, a dynamic weighing of a dried structured soil sample once immersed in water. The objective of this work was threefold: we aimed to (i) derive indicators from QST curves to evaluate soil structural stability, (ii) establish the relationship between soil properties and QST indicators, and (iii) assess how QST indicators respond to contrasting soil management practices. To reach these goals, we sampled the soil of 35 plots from three long-term field trials in the silt loam region of Belgium dealing respectively with contrasting organic matter inputs, tillage and P–K fertilisation. For each plot, indicators calculated from QST curves (e.g. total relative mass loss, disaggregation speed and time to meet a threshold values of mass loss) were compared to the results of the three tests of Le Bissonnais1996), used as a reference method for the measurement of soil aggregate stability.
Shortly after immersion in water, soil mass increases due to the rapid replacement of air by water in soil porosity. Then soil mass reaches a maximum before decreasing, once mass loss by disaggregation exceeds mass gain by air loss. Our results confirmed that the early mass loss under water is mainly related to slaking, whereas after a longer time period, clay dispersion and differential swelling become the dominant processes of soil disaggregation. The overall soil structural stability was positively correlated to the soil organic carbon (SOC) content and negatively correlated to the clay content of soil. Consequently, the SOC : clay ratio was closely related to QST indicators. Nevertheless, for a similar mean annual carbon (C) input, green manure and crop residues were more efficient in decreasing clay dispersivity and differential swelling, whereas farmyard manure promoted SOC storage and was more efficient against slaking. QST curves had a strong discriminating power between reduced tillage and ploughing regardless of the indicator, as reduced tillage increases both total SOC content and root biomass in the topsoil.The QST has several advantages. It (i) is rapid to run, (ii) does not require expensive equipment or consumables, and (iii) provides a high density of information on both specific mechanisms of soil disaggregation and the overall soil structural stability. As an open-access programme for QST data management is currently under development, the test has a strong potential for adoption by a widespread community of end users.Chromium (Cr) soil pollution is a pressing global concern that demands thorough assessment. The pollution-induced community tolerance (PICT) methodology serves as a highly sensitive tool capable of directly assessing metal toxicity within microbial communities. In this study, 10 soils exhibiting a wide range of properties were subjected to Cr contamination, with concentrations ranging from 31.25 to 2000 mg Cr kg−1, in addition to the control. Bacterial growth, assessed using the [3H]-leucine incorporation technique, was used to determine whether bacterial communities developed tolerance to Cr, i.e. PICT to Cr in response to Cr additions to different soil types. The obtained results revealed that at concentrations of 1000 or 2000 mg Cr kg−1, certain bacterial communities showed inhibited growth, likely attributable to elevated Cr toxicity, while others continued to thrive. Interestingly, with Cr concentrations below 500 mg Cr kg−1, bacterial communities demonstrated two distinct responses depending on soil type: 7 of the 10 studied soils exhibited an increased bacterial community tolerance to Cr, while the remaining 3 soils did not develop such tolerance. Furthermore, the Cr level at which bacterial communities developed tolerance to Cr varies among soils, indicating varying levels of Cr toxicity between studied soils. The dissolved organic carbon (DOC) and the fraction of Cr extracted with distilled water (H2O-Cr) played an essential role in shaping the impact of Cr on microbial communities (R2=95.6 %). These factors (DOC and H2O-Cr) contribute to increased Cr toxicity in soil, i.e. during the selection phase of the PICT methodology.
Increasing soil organic carbon is promoted as a negative emission technology for the agricultural sector with a potential co-benefit for climate adaptation due to increased soil water retention. Field-scale hydrological models are powerful tools for evaluating how the agricultural systems would respond to the changing climate in upcoming years and decades, for predicting impacts, and for looking for measures that would help decrease drought-driven crop stress under current and future climatic conditions. We quantified how different levels of soil organic carbon (SOC) additions at varied soil depths are expected to influence drought-induced transpiration reduction (Treddry) in maize cultivated in Switzerland. Parameterization of the model based on a pedotransfer function (PTF) was validated against soil moisture data from a long-term lysimeter experiment with a typical Swiss soil, and the model was subsequently applied under climate forcing between 1981 until 2099, representative of three distinct climatic sites of Switzerland. We used the same PTF to indirectly assess the effects of SOC additions at different depths on soil hydraulic properties. We found a threshold in both the added amount of SOC (2 % added) and the depth of sequestering that SOC (top 65 cm), beyond which any additional benefit appears to be substantially reduced. However, adding at least 2 % SOC down to at least 65 cm depth can reduce Treddry
In this technical note, we introduce a web-based application, the BonaRes Knowledge Library (KLIB, https://klibrary.bonares.de, last access: 26 July 2023), for the compilation and classification of scientific publications on soil processes according to the specific site conditions and experimental boundary conditions. The tool was developed based on the understanding that experimental findings in soil science are highly dependent on soil type, land use, and climate. The KLIB, therefore, goes beyond other available digital libraries by providing metadata on the site conditions and experimental settings for each publication. A number of visualization tools have been developed in the form of graphical networks to illustrate, for example, publications sharing the same type of scientific questions or soil properties that are affected by different types of drivers. This should help to explore the contents of the literature database more efficiently in order to support and facilitate the literature search efforts of the users. The KLIB is designed as a collaborative effort to encourage soil scientists to participate by entering their own studies and extending the existing database.